Definitions of Special Terms Herein Used
(1) "Metal-based Urushi Ware" means lacquered (or japanned) wares whose substrate comprises a metal such as aluminum, iron, gold or silver (in the present invention, the substrate is made of titanium).
(2) "Makie" means lacquered or urushi arts and crafts on which a picture, a pattern or the like is depicted with urushi, a powder of gold, silver or the like is spread over the surface, and the surface is further processed by, for instance, coating with a transparent layer and polishing it.
(3) "Raden" is a lacquered or japanned art or craft (urushi wares or the like) wherein small pieces of turban shell, ear shell, pearly oyster shell or the like are set in the surface so that the gloss side (inside) of the shell is exposed.
(4) "Hyomon, Heidatsu or Kanagai" is a kind of lacquering method or products obtained by such a method, the method being the same as that used in Raden except that a small thin plate or foil of a metal such as gold, silver or tin is used in place of small pieces of shell.
(5) "Kyushitsu" means a method of coating a substrate with urushi or products obtained by such a method.
(6) "Kurome" means the removal of moisutre from raw liquid urushi by irradiating the surface thereof with radiant heat with stirring.
(7) "Natsume" is a kind of container for storing green tea for presenting it and having a shape like a jujube or Chinese date.
(8) "Kuroroiro-nuri or -coating" is a black-colored urushi without drying oil or a method using such urushi.
(9) "Tame-nuri or -coating" is a kind of lacquering method or products obtained by coating a base with cinnabar red or the like, followed by applying a transparent urushi on the coating, drying it, and polishing it.
(10) "Shunkei-nuri or -coating" means a kind of lacquering or japanning method in which a wooden base is colored or pigmented yellow, red or the like and then a transparent lacquer or urushi is applied on the surface so that the texture of the wooden base can be seen through the lacquer layer.
(11) "Kijiroiro-nuri or -coating" is the same as Shunkei-nuri except that the wooden base is not colored or pigmented.
Metals such as iron, brass, aluminum and alumite are used in place of wood base material in Makie.
However, when urushi wares are formed using iron and brass as base materials, various problems arise during preparation of such an urushi ware-like product. For instance, these metals have a very high specific gravity and they are susceptible to corrosion if they come in direct contact with air. Thus, their applications as the base material for making urushi ware-like products is limited to a very narrow range from the viewpoint of manufacture. On the other hand, when alumite and aluminum are used as the base material, these metals are light and show high strength and, therefore, they can provide excellent products. However, aluminum and alumite per se have silver-covered surfaces and hence do not provide any particular aesthetic effect, and if they are used in such a condition that they come in contact with air, they are corroded by acids, alkalis or air itself.
In general, a coated film of, for instance, urushi has many pinholes. Therefore, water or moisture can diffuse through such pinholes and reach the base material even if it is covered with such a coated film, and thus the base material suffers corrosion. For this reason, conventional metallic base materials are susceptible to corrosion, and the film coated thereon is liable to be peeled off and hence the durability thereof is impaired. As a result, metals such as iron and brass have not been used as the base material for manufacturing products coated with urushi. Furthermore, metals such as aluminum and alumite, which show high strength and are light, are used as a mere substrate, and they are seldom used in such a manner that a part thereof is exposed to serve as a decorative portion.
A technique is known which comprises heating titanium or titanium alloy materials at 900.degree. C. to 1300.degree. C. in vacuo to grow crystal grains on the surface of the material while simultaneously thermally etching the surface, and then anodizing it, to develop interference multi-color on the metal surface (Japanese Patent Publication for Opposition Purpose, hereunder refereed to as "J. P. KOKOKU," No. Sho 53-23773 published in 1978).